[syslinux] Nested PXELINUX configurations

[Giannis Roussos]

I discovered di-netboot-assistant , which worked as advertised. The .cfg 
files it produced all have absolute paths without ::.

Giannis

On 24/3/2011 9:27 μμ, Gene Cumm wrote:
> On Thu, Mar 24, 2011 at 12:59, Giannis Roussos
> <morpheus at csl.mech.ntua.gr>  wrote:
>> Hello all,
>
> Comments inline; solution near the bottom.
>
>> I have a boot server (running Debian Lenny x64) with a number of bootable
>> options already configured (freedos, memtest, sysresccd etc).
>>
>> What I am struggling to do now is add Ubuntu and Debian netinst images so
>> that I can boot from the network and have all the boot options available as
>> if I was using a CD-ROM.
>>
>> The problem is that (as far as I can tell) the Ubuntu and Debian PXELINUX
>> assume that they are located in the tftp root folder. Since however Debian
>> and Ubuntu use a similar file structure, I cant have both distros a the same
>> time in the tftp root. (Not to mention the mess this would create in the
>> tftp root).
>
> The structure of the configs is an issue for everything but PXELINUX.
> PXELINUX actually uses "::" as the character to indicate a root
> directory.
>
>> Idealy I would like to place each distro in a separate folder inside tftp
>> root (see below) and "chainload" each pxelinux configuration from the
>> default config file.
>>
>> TFTP_root---pxelinux.cfg--->default
>>     |
>>     |-------debian------pxelinux.cfg----->default
>>     |
>>     |-------ubuntu------pxelinux.cfg----->default
>>
>> Since PXELINUX uses (AFAIK) absolute paths, there are two ways to achieve
>
> It never uses absolute paths as I mentioned in the post you linked below.
>
>> something like this:
>> 1) Edit all configuration files and add the correct path in all include
>> arguments. I have done it for Ubuntu and it works but is not practical at
>> all, requiring a lot of work for each new release.
>> 2) Find the correct kernel, initrd etc settings for the Ubuntu/Debian
>> options and add them to the main PXELinux config or a submenu. Again, this
>> requires a lot of work to add all the options and the graphics/help of each
>> distro wouldn't be available.
>>
>> None of the above options is nice and practical, nor allows me to easily
>> update to newer releases without a lot of work.
>> Thus, I was wondering if there is some way to chainload the COMPLETE
>> PXELINUX config of each distro from separate folders. Maybe some option to
>> "chroot" pxelinux so that all files are automaticaly loaded from the nested
>> folder?
>>
>> I have tried copying pxelinux.0 in each of the distros' folders and load
>> this as a new kernel, but the pxelinux cfg in the tftp root is loaded still.
>> Directly loading the main cfg file does not work either since all the
>> included files are not in the tftp root.
>
> Don't use it as a kernel.  Try the following:
>
> LABEL debian
>    COMBOOT pxechain.com
>    APPEND ::debian/pxelinux.0
>
> Please note that if the first PXELINUX is version 4.xx, it must be at
> least version 4.04-pre1 as there is a bug that was resolved in
> 4.04-pre1.  I believe 4.04-pre14 is OK but I can't be certain at this
> time.  For a production environment, I'd advise waiting for 4.04.
> Otherwise, try 3.86 for now.
>
>> The same question has been asked here
>> http://web.archiveorange.com/archive/v/mwjwmJ0CIqkvn1V88yus but no complete
>> answer has been given.
>>
>> Thanks for all the help,
>> Giannis
>
> I thought that it was.  I also think that the above post is a little different.
>


-- 
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  Giannis P. Roussos
  PhD Student
  Control Systems Lab, Mechanical Eng. Dept.
  National Technical University of Athens
  9 Heroon Polytechniou Str., Zografou
  Athens 15700, Greece

  Tel : ++30-210-772-1726
  e-mail : jrous at mail.ntua.gr
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